Fatty acid hydroperoxide lyase (HL) is an enzyme of the octadecanoid pathway that cleaves a C—C bond in the hydroperoxides of polyunsaturated fatty acids to generate aldehydes and ω-oxo-acids. This enzyme is widely distributed in plants and is involved in the biosynthesis of volatile aldehydes and alcohols. Its presence in plants can be recognized by the fact that crushed leaves of nearly every plant generate a grassy smell that is characteristic of C6-aldehydes. The short-chain volatile aldehydes and their reduced derivatives, alcohols, are important constituents of the characteristic flavors of fruits, vegetables and green leaves.
The six-carbon volatile compounds, leaf aldehyde [(2E)-hexanal] and leaf alcohol [(3Z)-hexanol], are important components of the aroma and flavor of fruits and vegetables and are associated with ‘green notes’ of leaves. These compounds are widely used as flavors in foods and beverages and some of the C6-aldehydes are also reported to have anti-microbial properties. These volatile compounds are produced by fatty acid hydroperoxide lyase (HL) by cleaving 13-hydroperoxy fatty acids, mainly from linolenic and linoleic acids.
Commercial production of natural ‘green note’ compounds is generally achieved by fractional distillation of essential oils such as mint oil or by the combined action of lipoxygenase and hydroperoxide lyase on unsaturated fatty acids using plant material from different sources. These processes provide low yields and are dependant on specific plant materials. Therefore, there is a need for improved methods of generating ‘green note’ compounds.